TWI731558B - Variable resistor - Google Patents

Abstract

The subject of the present invention is to provide a variable resistor capable of stably holding oil on the surface of the resistor without forming the surface of the resistor in an uneven shape. The variable resistor 50 of the present invention includes: a substrate 1; a resistor 5 arranged on the substrate 1; an oil 11 coated on the surface 5S of the resistor 5; and a sliding member 9 coated with the oil 11 The surface 5S of the resistor body 5 slides; and the output of the variable resistor 50 changes with the change of the contact position of the sliding member 9 and the resistor body 5; The side of 5 surrounds at least a part of the resistor 5 in a plan view, and the surface free energy is smaller than that of the resistor 5.

Description

Variable resistor

The present invention relates to a variable resistor used as a position detection device, etc., which changes the resistance value by the movement of a sliding member on the surface of a resistor.

The variable resistor includes a substrate provided with a resistor, and a sliding member that moves (slides) on the resistor while in contact with the surface of the resistor. As the sliding member slides on the resistor including the conductor, the relative position changes, and the resistance value of the circuit connected to the two changes. Therefore, the variable resistor can detect the position of the external moving body linked to the sliding member based on the voltage that changes in accordance with the resistance value, for example.

In variable resistors, in order to improve the reliability achieved by reducing sliding noise (micro-linearity) and the wear resistance when the sliding body rubs on the surface of the resistor body, oil is applied to the surface of the resistor body, etc. The situation of the lubricant. In this case, in order to maintain the lubricating effect, it is necessary to keep oil on the surface of the resistor. For example, Patent Document 1 describes a position sensor in which at least a part of the surface of the resistor (film) is formed in an uneven shape. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] JP 2007-317971 A

[The problem to be solved by the invention]

However, the position sensor described in Patent Document 1 has a problem of slight linear deterioration due to the fact that a part of the surface of the resistor is formed into a concave-convex shape, and the resistance value changes within a small range. In addition, the formation of a specific uneven shape on the surface of the resistor also has a problem of lowering the production efficiency. The object of the present invention is to provide a variable resistor capable of stably holding oil on the surface of the resistor body without forming an uneven shape on the surface of the resistor body. [Technical means to solve the problem]

The variable resistor of the present invention includes: a substrate; a resistor body arranged on the substrate; oil applied on the surface of the resistor body; and a sliding member that slides on the surface of the resistor body coated with the oil ; And the output of the variable resistor changes with the change of the contact position of the sliding member and the resistor; it is characterized by having: an oil-repellent portion, which is in a plan view from the side of the resistor on which the substrate is arranged, At least a part of the aforementioned resistor is surrounded, and the surface free energy is smaller than that of the aforementioned resistor. By being surrounded by the oil-repellent part whose surface free energy is smaller than that of the resistor, a film of oil can be maintained on the surface of the resistor.

The aforementioned oil only needs to have a weight average molecular weight of 2000 or more and a dynamic viscosity at 20°C of 40 [mm ² /s] or more. By using oil with this property, the change in the total resistance of the resistor can be suppressed. The surface free energy of the oil repellent portion is preferably 50 [mJ/m ² ] or less. The aforementioned oil-repellent portion is preferably formed using a resin paste based on epoxy resin. Due to these structures, the oil repellency of the oil repellent portion becomes higher, so that the film of oil with lower dynamic viscosity can be stably maintained on the surface of the resistor.

The oil-repellent portion is preferably arranged to surround the periphery of the resistor body along the periphery of the resistor body in a plan view. The height from the surface of the substrate to the surface of the oil repellent portion is preferably greater than the height from the surface of the substrate to the surface of the resistor. Preferably, the oil-repellent portion has an overlapping portion arranged on the surface of the resistor body. With these structures, the oil film can be prevented from spreading between the resistor body and the oil repellent portion, and the oil film can be stably maintained on the surface of the resistor body. [Effects of Invention]

The variable resistor device of the present invention prevents oil on the surface of the resistor from flowing to parts other than the surface of the resistor by arranging an oil-repellent portion with less oil wettability around the resistor. Therefore, it is possible to stably retain oil on the surface of the resistor without forming uneven shapes on the surface of the resistor.

The embodiments of the present invention will be described below with reference to the drawings. In each figure, the same reference numeral is given to the same member, and the description is omitted as appropriate.

Fig. 1(a) is a plan view schematically showing the main part of a variable resistor as an embodiment of the present invention, and Fig. 1(b) is a cross-sectional view taken along the line A-A in Fig. 1(a). Figure 2 is an exploded perspective view showing the variable resistor. The variable resistor 50 is formed by the substrate 1, the knob member 8, the sliding member 9 and the shaft member 10. The substrate 1 has a circular first base 1a and a second base 1b projecting in a rectangular shape from the first base 1a, and a center hole 1c is provided in the center of the first base 1a.

The substrate 1 has a resistor 5 formed on its surface, and includes an insulating molded body mainly composed of a phenol laminate substrate, a glass-containing epoxy substrate, a molded resin substrate, a ceramic substrate, and the like.

On the surface of the first base 1a, a current collector 4 containing a conductive material containing silver or the like is provided in a ring shape around the center hole 1c. The terminal 2 is connected to the lower surface of the collector 4 (the surface on the Z1-Z2 axis Z2 side), and the collector 4 and the terminal 2 are set to the same potential.

A resistor 5 in the shape of an arc including a part of a circular ring is provided on the outer periphery of the collector 4. The ends 5a, 5b of the resistor 5 are electrically connected to the terminals 3a, 3b via electrodes 6A, 6B, respectively, and the terminals 3a, 3b and the ends 5a, 5b of the resistor 5 are respectively set to the same potential.

The resistor 5 is generally formed of a resistive paste obtained by dispersing a conductor such as carbon black in a binder resin dissolved in a suitable solvent and adding a solvent as needed. The resist 5 is formed by forming a pattern of a specific shape with a resistive paste using well-known screen printing or the like. When forming the resistor 5, it may be dried as necessary to remove the solvent and baked.

As the binder resin of the resistive paste, phenol resin, polyimide resin, etc. are used in order to impart heat resistance and the like. In addition, in the resistive paste, in order to impart abrasion resistance and the like, it is preferable to blend fillers such as carbon fiber and silica. Furthermore, in addition to the above-mentioned materials, additives such as defoamers may be added to the resistive paste forming the resistor 5.

When the resistor body 5 is formed in an arc shape (horseshoe shape) as shown in FIG. 1(a), FIG. 1(b), and FIG. 2, the sliding member 9 is slid relative to the substrate 1 along the resistor body 5. Can be installed rotatably. In this way, the rotary variable resistor 50 is obtained. However, the pattern of the resistor 5 is not limited to the arc shape. For example, in the case of being formed into an elongated shape, the sliding member 9 is slidably mounted with respect to the substrate 1 in a manner of sliding along the resistor body 5 to obtain a sliding variable resistor 50.

Generally, before installing the resistor 5, a pair of electrodes 6A and 6B are provided by screen printing a conductive paste such as silver on the substrate 1 or the like. The pair of electrodes 6A, 6B are connected with a pattern of a resistor body 5 having an arc shape or the like, and electrodes 6A, 6B are provided at both ends 5a, 5b of the resistor body 5. The resistor 5 is preferably arranged to cover the electrodes 6A and 6B from above.

As shown in FIG. 1(a) and FIG. 1(b), oil 11 is applied to the surfaces of the current collector 4 and the resistor 5. The oil 11 functions as a lubricant for improving the abrasion resistance of the surfaces of the current collector 4 and the resistor body 5. For example, a fluorine-based oil can be used. Examples of fluorine-based oils include perfluoroalkyl polyethers, perfluoropolyethers, etc., and either linear type or side-chain type may be used.

The oil 11 may be mixed with other oils or additives as needed, but in the material constituting the fluorine-based oil, for example, it is preferable that 80% by weight or more is fluorine-based oil, and more preferably 100% by weight.

Based on the viewpoint that the oil 11 functions as a lubricant to prevent the performance of the variable resistor 50 from deteriorating, the film thickness of the oil 11 formed in a layer on the resistor 5 (in the Z1-Z2 axis direction of FIG. 1(b)) The thickness) is preferably 0.07 μm or more, more preferably 0.2 μm or more, and most preferably 0.8 μm or more. From the viewpoint of maintaining stable contact between the resistor 5 and the sliding member 9, it is preferably 3 μm or less.

The weight average molecular weight of oil 11 is preferably 2000 to 18000, more preferably 4500 to 18000. The kinematic viscosity at 20°C is preferably 40 to 500 [mm ² /s] (cSt), more preferably 150 to 500 [mm ² /s].

The type of oil 11 used as a lubricant is not limited. Examples of commercially available products that can be used as oil 11 include: Solvay Specialty Polymers, Fomblin series; Daikin Industrial, DEMNUM series; Chemours, Krytox series; Moresco, Moresco phospharoll, and the like.

As shown in Fig. 1(a) and Fig. 1(b), the oil-repellent portion 15 is in a plan view from the side (Z1 side of the Z-Z2 axis of Fig. 1(b)) where the substrate 1 is arranged on the resistor body 5, It is arranged to surround at least a part of the resistor body 5. Since the oil-repellent portion 15 has a smaller surface free energy (surface tension) than the resistor 5, it is difficult to wet by the oil 11 (hereinafter, appropriately referred to as "low wettability"). By repelling the oil 11 by the oil-repellent portion 15 surrounding the resistor body 5, the flow of the oil 11 on the surface of the resistor body 5 can be suppressed, and the oil 11 can be kept on the surface of the resistor body 5. Therefore, even when the oil 11 has a low molecular weight and a low dynamic viscosity, the oil 11 can be held on the surface of the resistor 5 and maintained at a specific film thickness. Therefore, for example, a low molecular weight and low dynamic viscosity oil 11 with a weight average molecular weight of 2000-5500 and a dynamic viscosity of 40-70 [mm ^{2 /s] (cSt) at 20° C. can be used.}

From the viewpoint of holding the oil 11 on the surface of the resistor 5, it is assumed that the wettability of the oil repellent portion 15 is smaller than that of the resistor 5. The surface free energy of the oil repellent portion 15 is preferably 50 [mJ/m ² ] or less, and more preferably 40 [mJ/m ² ] or less. The surface free energy is a value calculated based on the contact angle of three liquids (water, bromonaphthalene, ethylene glycol) whose surface free energy is a known value based on Kitazaki Hata's theory.

The oil-repellent portion 15 is generally formed by a resin paste obtained by adding additives such as a dye or a defoaming agent to a resin dissolved in an appropriate solvent as needed. A pattern of a resin paste of a specific shape is formed on the surface of the resistor 5 by well-known screen printing or the like to form the oil-repellent portion 15. When forming the oil-repellent portion 15, the solvent can be removed and baked by drying as needed. The resin containing the most in the resin paste used for the formation of the oil-repellent portion 15 is appropriately referred to as "basic resin".

Specific examples of the resin contained in the resin paste include thermosetting resins such as epoxy resin, polyimide, and melamine, thermoplastic resins such as polyethylene, polypropylene, polystyrene, and polycarbonate, and Light-curable resin. From the viewpoint of forming the oil-repellent portion 15 with a lower surface free energy, a resin with a lower content of -OH is preferred, and a resin without -OH is more preferred. In addition, from the viewpoint of resistance to oil 11, a thermosetting resin is preferable.

The oil-repellent portion 15 is arranged in a plan view (when the XY plane of the substrate 1 of FIG. 1(a) is viewed from the Z1 side of FIG. 1(b)), and is arranged to surround the periphery of the resistor 5 along the periphery 5E of the resistor 5. The oil-repellent portion 15 can maintain the state where the entire surface of the pattern of the resistor 5 is covered by the layer of oil 11.

As shown in FIG. 1(b), the oil-repellent part 15 is connected to the peripheral edge 5E of the resistor body 5, and is provided. Here, "provided in connection with the peripheral edge 5E" means that the peripheral edge 5E of the pattern of the resistor 5 is in contact with the oil-repellent portion 15, and there is no gap for the flow of the oil 11 between the two. With this configuration, it is possible to prevent the oil 11 from flowing out of the gap between the peripheral edge 5E and the oil repellent portion 15, and maintain the state where the film of the oil 11 is formed on the surface of the resistor body 5 with a specific film thickness.

The height from the surface 1S of the substrate 1 to the surface 15S of the oil-repellent portion 15 (the film thickness in the Z1-Z2 axis direction of the oil-repellent portion 15) h1 is greater than the height from the surface 1S of the substrate 1 to the surface 5S of the resistor 5 (resistance The film thickness in the Z1-Z2 axis direction of the body 5) h2. Therefore, the oil-repellent portion 15 not only uses the function based on the difference in surface free energy from the resistor 5, but also uses the function based on the difference in height from the surface 1S of the substrate 1 to stably maintain the oil on the surface of the resistor 5. 11.

For example, when the film thickness of the resistor 5 is about 10 to 15 μm, the film thickness in the Z1-Z2 axis direction of the oil repellent portion 15 is preferably about 20 to 50 μm. The above-mentioned difference between the height h1 and the height h2, that is, the height X from the surface 5S of the resistor body 5 to the surface 15S of the oil-repellent portion 15 is preferably 10-40 μm, more preferably 15-35 μm, and most preferably 20 ～30 μm.

The oil-repellent portion 15 has an overlapping portion 15L arranged on the surface of the resistor body 5. The overlapping portion 15L refers to the portion provided on the surface of the resistor 5 that overlaps the resistor 5 when the substrate 1 is viewed from the Z1 side of the Z1-Z2 axis in FIG. 1(b). By providing the overlapping portion 15L on the surface of the resistor body 5, even if a slight position shift occurs during screen printing, the oil-repellent portion 15 and the resistor body 5 are connected and formed without a gap. Therefore, it is possible to prevent the oil 11 on the surface of the resistor body 5 from flowing out from between the oil repellent portion 15 and the resistor body 5 to a part other than the surface of the resistor body 5.

As shown in Fig. 2, the knob member 8 is formed into a disc shape with an insulating material, and a hole 8a is provided in the center thereof. In addition, an uneven portion 8b is formed on the outer edge of the knob member 8. The uneven portion 8b prevents slippage between the member that imparts rotation and the outer edge when the knob member 8 is imparted with rotation.

A sliding member 9 made of a metal leaf spring such as phosphor bronze is fixed to the lower part of the knob member 8. In addition, the sliding member 9 has: a sliding member 9a that gently presses the surface of the current collector 4 while sliding; and a sliding member 9b that gently presses the surface of the resistor body 5 while sliding. In addition, the parts of the slider 9a and the slider 9b that are in contact with the collector 4 and the resistor 5 are sliding contacts.

As the sliding member 9, a noble metal material that can maintain good contact with the resistor 5 even under long-term sliding is used. Specifically, the surface of nickel-silver (copper-zinc-nickel alloy) can be plated with gold or silver, or an alloy such as palladium, silver, platinum, or nickel can be used. Especially when there is a concern about surface oxidation at high temperatures, in order to maintain a stable contact state, it is better to use a precious metal alloy.

The shaft member 10 is inserted into the hole 8a of the knob member 8 and the center hole 1c of the base plate 1, and the front end of the shaft member 10 is held on the back side of the base plate 1 to prevent the shaft member 10 from falling off the center hole 1c of the base plate 1. The knob member 8 is opposed to the base plate 1 and can rotate integrally with the sliding member 9.

When the knob member 8 is rotated, the sliders 9a and 9b of the sliding member 9 will slide on the surfaces of the collector 4 and the resistor body 5, respectively, so that the resistance value between the terminal 2 and the terminals 3a and 3b is variable. Since the resistance value can be used to detect the position of the external moving body linked with the rotation of the knob member 8, the variable resistor 50 can be used as a position detection device. In addition, a constant voltage can be applied between the terminal 3a and the terminal 3b, and the potential of the position where the slider 9b is in contact is used as an output, and the position can be detected based on the change in the output voltage.

Fig. 3(a) is a plan view schematically showing a modification of the main part of the variable resistor as an embodiment of the present invention, and Fig. 3(b) is a cross-sectional view taken along the arrow A-A in Fig. 3(a). As shown in these figures, the oil-repellent portion 15 may be configured to include only the overlapping portion 15L arranged on the surface of the resistor body 5. Fig. 4(a) is a plan view schematically showing another modification of the main part of the variable resistor as an embodiment of the present invention, and Fig. 4(b) is a cross-sectional view taken along the arrow A-A in Fig. 4(a). As shown in these figures, the oil-repellent portion 15 may also be configured without the overlapping portion 15L arranged on the surface of the resistor body 5. In this case, the height h2 from the surface of the substrate to the surface of the oil repellent portion 15 is configured to be greater than the sum of the height h1 from the surface of the substrate to the surface of the resistor and the film thickness of the oil 11 (h2>h1+oil film thickness). [Example]

Hereinafter, the present invention will be explained more specifically using examples and the like, but the scope of the present invention is not limited to those examples and the like.

(Example 1) A resistor body with an oil repellent portion was coated with an amount of oil with an initial oil film thickness of 1.2 μm, and the oil film thickness on the surface of the resistor body after the high temperature standing test (after 86 hours) was measured. Resistors are formed on the substrate using resin paste (the conductor is carbon black and graphite, and the binder resin is phenol resin). The height h2 from the surface of the substrate to the surface of the resistor (refer to Figure 1(b)) is set to 12 to 13 μm. The surface free energy of the resistor is 54.6 [mJ/m ² ].

The oil-repellent part is formed by a resin paste containing an epoxy resin with a concentration of about 60% by weight as the basic resin. Set the height h1 from the surface of the substrate to the surface of the oil repellent part to 36-38 μm, and set the difference X between h1 and the height h2 of the resistor to 23-26 μm (refer to Figure 1(a) and Figure 1(b)) , The oil repellent is formed by surrounding the resistor body. The surface free energy of the oil-repellent part is 39.9 [mJ/m ² ].

＜Comparative Examples 1～3＞ Except for the point that the oil-repellent part is not provided, the same resistor body as in Example 1 is formed. Coat the surface of the resistor with the same oil as in Example 1 so that the film thickness becomes 0.7 μm, 1.2 μm, and 1.6 μm (comparative examples 1, 2, 3), and measure the resistance after the high temperature standing test (86 hours later) The thickness of the oil on the surface of the resistor.

＜Test method＞ As a standing test under high temperature conditions assuming long-term storage, after standing at 128°C for 86 hours, the film thickness of the oil present on the surface of the resistor is measured. At the same time, visually confirm the state of the surface of the resistor after the test. The posture of the variable resistor when placed under high temperature conditions is assumed that the XY plane of the substrate 1 (refer to Fig. 1(a)) becomes the vertical direction.

Table 1 and FIG. 5 show the measurement results of Example 1 and Comparative Examples 1 to 3. [Table 1] Oil film thickness (μm) Surface condition (visual inspection) initial After high temperature test After high temperature test Example 1 1.2 0.86 Dark color Comparative example 1 0.7 0.01 Light color Comparative example 2 1.2 0.04 Light color Comparative example 3 1.6 0.05 Light color

The resistor body of the variable resistor of Example 1 is the same even after the high temperature test. The surface of the oil-coated resistor body has a darker color and maintains a wet state. In addition, the film thickness of the oil on the surface of the resistor body maintains a film thickness sufficient for exhibiting a lubricating function. From this result, it can be seen that by providing the oil-repellent portion so as to surround the pattern of the resistor, the film thickness of the oil formed on the surface of the resistor can be maintained for a long period of time under high temperature conditions. In contrast, the resistance bodies of the variable resistors of Comparative Examples 1 to 3 are all coated with oil. The surface color of the resistor body is thin, and the wet state is not maintained. In addition, the film thickness of the oil on the surface of the resistor is not a film thickness sufficient for exhibiting a lubricating function.

According to the graph of weight loss at 120°C and 150°C shown in Figure 6, it is believed that the evaporated oil is about 10-20% in the high temperature standing test at 128°C for 86 hours. In contrast, in Comparative Examples 1 to 3, after the high-temperature standing test, the oil loss on the surface of the resistor body was 90% or more. Based on these circumstances, it is believed that the reason for the loss of oil on the surface of the resistor body is that the fluidity of the oil increases and moves to a part different from the surface of the resistor body, rather than the evaporation of the oil. The variable resistor of Example 1 can be said to suppress the flow of oil by enclosing the oil repellent portion of the resistor body, so that the oil film can be maintained on the surface of the resistor body.

<Comparative example 4> Except that the resin paste used to form the oil-repellent portion was changed as follows, the standing test under high temperature conditions was carried out in the same manner as in Example 1. A resin paste containing about 50% by weight of xylene resin as the base resin was used instead of the resin paste of Example 1. The surface free energy of the oil-repellent part is 136.9 [mJ/m ² ]. <Comparative Example 5> Except that the resin paste used to form the oil-repellent portion was changed as follows, the standing test under high temperature conditions was carried out in the same manner as in Example 1. A resin paste containing a phenol resin with a concentration of about 40% by weight as the basic resin was used instead of the resin paste of Example 1. The surface free energy of the oil repellent is 159.8 [mJ/m ² ].

Table 2 and FIG. 7 show the measurement results of Example 4 and Comparative Examples 2 to 5. [Table 2] Oil film thickness (μm) Surface condition (visual inspection) initial After high temperature test After high temperature test Example 1 1.2 0.86 Dark color Comparative example 4 1.2 0.05 Light color Comparative example 5 1.2 0.05 Light color

In the case of using a resin paste with phenol or xylene as the base resin to form the oil-repellent part, the film thickness of the oil cannot be sufficiently maintained on the surface of the resistor after the test at high temperature. It is considered that the oil repellent parts of Comparative Examples 4 and 5 have higher surface free energy than the resistor body and better wettability with oil, so that the oil on the surface of the resistor body cannot be prevented from flowing to parts other than the surface of the resistor body. On the other hand, the oil repellent part of Example 1 formed with a resin paste based on epoxy resin has a smaller surface free energy than a resistor. Therefore, it can be said that the oil repelling effect of the oil-repellent part, which is poorly wetted with oil, can inhibit the oil on the surface of the resistor from flowing to other parts. Based on these results, it can be said that in order for the oil-repellent part provided to surround the resistor body to function as a barrier preventing the oil on the surface of the resistor body from flowing to other parts, it is necessary to make the surface free energy smaller than that of the resistor body. Poor wetting with oil. Therefore, as the basic resin of the resin paste forming the oil-repellent part, it is preferable to use a resin having the property of repelling oil. [Industrial availability]

The present invention is a variable resistor with high reliability under high temperature conditions, for example, it can be used as a position detection device.

1: substrate 1a: first base 1b: 2nd base 1c: Center hole 1S: Surface 2: terminal 3a: Terminal 3b: Terminal 4: Collector 5: Resistor body 5a: end 5b: end 5E: Perimeter 5S: Surface 6A: Electrode 6B: Electrode 8: Knob component 8a: hole 8b: Concave and convex part 9: Sliding member 9a: Slide 9b: Slider 10: Shaft member 11: oil 15: Oil Removal Department 15L: Overlap 15S: surface 50: Variable resistor A-A: Arrow h1: height h2: height X: height/difference Z1-Z2: axis

Fig. 1(a) is a plan view schematically showing the main part of a variable resistor as an embodiment of the present invention; Fig. 1(b) is a cross-sectional view taken along the line A-A in Fig. 1(a). Fig. 2 is an exploded perspective view showing the variable resistor as the embodiment of the present invention. Fig. 3(a) is a plan view schematically showing a modification of the main part of the variable resistor as an embodiment of the present invention; Fig. 3(b) is a cross-sectional view taken along the arrow A-A in Fig. 3(a). Fig. 4(a) is a plan view schematically showing another modification of the main part of the variable resistor as an embodiment of the present invention; Fig. 4(b) is a cross-sectional view taken along the line A-A in Fig. 4(a). Fig. 5 is a graph showing the measurement results of Example 1 and Comparative Examples 1-3. Figure 6 is a graph showing the weight loss due to the heat of the oil analyzed by TG-DTA. Fig. 7 is a graph showing the measurement results of Example 1 and Comparative Examples 4 to 5.

1: substrate

1S: Surface

4: Collector

5: Resistor body

5E: Perimeter

5S: Surface

9: Sliding member

9a: Slide

9b: Slider

11: oil

15: Oil Removal Department

15L: Overlap

15S: surface

50: Variable resistor

A-A: Arrow

h1: height

h2: height

X: height/difference

Z1-Z2: axis

Claims (4)

A variable resistor comprising: a substrate; a resistor body arranged on the substrate; oil coated on the surface of the resistor body; and a sliding member that slides on the surface of the resistor body coated with the oil ; And the output of the variable resistor changes with the change of the contact position of the sliding member and the resistor; it is characterized by having an oil-repellent portion, which is in a plan view from the side of the resistor on which the substrate is disposed , Surrounding at least a part of the resistor body, and the surface free energy is smaller than that of the resistor body; the oil-repellent part is arranged to surround the resistor body along the periphery of the resistor body in a plan view, and has a surface disposed on the resistor body And the height from the surface of the substrate to the surface of the oil repellent part is greater than the height from the surface of the substrate to the surface of the resistor. Such as the variable resistor of claim 1, wherein the weight average molecular weight of the aforementioned oil is more than 2000, and the dynamic viscosity at 20°C is more than 40 [mm ² /s]. Such as the variable resistor of claim 1, wherein the surface free energy of the oil-repellent portion is 50 [mJ/m ² ] or less. Such as the variable resistor of claim 1, wherein the aforementioned oil-repellent portion is formed of a resin paste using epoxy resin as a basic resin.

Images